This invention relates generally to an ink ribbon cartridge for use in a recording device, and more specifically to a take-up spool for ink ribbon cartridges including a tube and clutch mechanism.
In a thermal ink ribbon cartridge, an ink ribbon is wound around a supply spool tube and extends to a take-up spool tube. An ink layer is formed on one surface of the ink ribbon. A spindle without a gear is provided at one end of each of the supply tube and the take-up tube while a spindle with a gear is provided at the other end of the supply tube and take-up tube. The spindles are selectively removable from the supply and take-up tubes.
At the time of ink ribbon replacement, each of the spindles is removed from a snap fit engagement with a corresponding hole in the housing of the ink ribbon cartridge. Then, the spindles are removed from their corresponding ends of the supply and take-up tubes. Replacement tubes with ink ribbon are installed onto the take-up and supply spindles and are reattached to the ink ribbon cartridge housing. Subsequently, the ink ribbon cartridge is mounted in a printer or facsimile system. If an ink ribbon is improperly mounted or the direction of winding is reversed from the proper direction, the ink ribbon cannot be wound up thus resulting in a failure in printing.
Existing cartridges use a clutching mechanism for an ink ribbon take-up tube which has three separate components, in addition to the tube, namely a gear, a hub and a tube insert. As shown in FIG. 1A, a take-up tube 10 has an opening 12 extending therethrough and one or two slots 14 in each end of the tube. The tube 10, which is made of cardboard, receives a plastic insert 20 which is inserted into the end of the tube and has tabs (not shown) which engage the slots 14 and snap the insert into place within the tube opening. The insert remains as part of the take-up tube. The insert has a lip 22 which engages an end surface of the cardboard tube. The insert has an opening 24 extending therethrough. Referring to FIG. 1B, at an end 26 of the insert, which is opposite the end with lip 22 are a series of drive surfaces 28 and slip surfaces 30 formed by angled slots 32 formed at equally spaced apart areas along a perimeter of the insert. The drive and slip surfaces extend axially inwardly from end surface 26 of the insert 20. The drive surfaces are substantially radial edges which form an abutment shoulder for drivingly engaging with a drive lug of a drive gear. The slip surfaces are smooth, tapered surfaces or slopes which have a chord component which allows the drive lug to slip along the surfaces.
A hub 40 is snap fit onto a drive gear assembly 50. The hub has several prongs 42 which extend axially from a flat disk surface 44 and extend into matching slots 52 in the drive gear. The prongs are then locked into place within the gear and attach the hub to the gear. The hub further comprises a central portion 46 having an opening 47 therethrough and an end portion 48 with a slot 49 therethrough. The drive gear assembly includes an elongated leg portion 54 which extends through the opening in the central portion of the hub. Portion 54 includes a cantilever member 56 which is formed between grooves in the leg portion. The cantilever member includes a drive lug 58 formed at an end thereof. The cantilever drive lug extends through opening 47 of the hub and protrudes through slot 49. The drive lug is formed of a resilient material and can be depressed radially inwardly toward the hub center as the hub and drive gear are installed together. Once the drive lug is fully received in the hub, it extends radially outwardly through the slot of the hub and is locked within the slot.
The drive gear and hub assembly are then inserted into the plastic insert 20 in the cardboard tube. The drive lug is again depressed radially inwardly as the hub is axially inserted through the opening 24 in the insert 20 until the lug reaches the drive and slip surfaces at the end of the insert. The lug remains depressed inwardly by the slip surfaces 30 and does not allow the cardboard tube to rotate with the drive gear. That is, the drive lug allows the drive gear and hub to rotate counter-clockwise (see FIG. 1B) with respect to the slip surfaces but does not engage or lock to the insert. The drive gear and hub rotate counter-clockwise with respect to the slip surfaces and do not engage the insert thus not rotating the cardboard tube.
However, if the hub and drive gear are rotated in the opposite direction, i.e. clockwise, the drive lug extends through one of the slots of the insert and engages one of the drive surfaces 28 thus rotating the insert and the cardboard tube in a clockwise manner in FIG. 1B. Thus, the cardboard tube and the take-up spool can only rotate in one direction as driven by the drive gear.
A problem with this existing design is that the end of the cardboard tube with the plastic insert can only accommodate the drive gear with the hub and drive lug. This end is not compatible with any of the spindles or other drive gear arrangements. Further, the design requires four parts and is structurally complex and expensive.
Thus, a one piece tube which accomplishes the same function of permitting rotation of the take-up tube in only one direction would be desirable. This tube would also be compatible with other drive gears and supply spindles. Furthermore, no separate insert would be required in the tube and the hub component can be eliminated. Accordingly, it is desirable to provide a new and improved take-up spool for an ink ribbon cartridge which would meet the above stated needs and others and provide better, more advantageous overall results.